1. Field of the Invention
The present invention relates to a radiation detecting apparatus incorporating a radiation conversion panel for detecting a radiation which has passed through a subject and converting the detected radiation into radiation image information, and a radiation image capturing system incorporating such a radiation detecting apparatus. The present invention is also concerned with a temperature compensating method for compensating a change in the temperature of a radiation conversion panel.
2. Description of the Related Art
In the medical field, there have widely been used radiation image capturing systems which apply a radiation to a subject and guide the radiation that has passed through the subject to a radiation conversion panel, which captures a radiation image from the radiation. Known forms of the radiation conversion panel include a conventional radiation film for recording a radiation image by way of exposure, and a stimulable phosphor panel for storing a radiation energy representing a radiation image in a phosphor and reproducing the radiation image as stimulated light by applying stimulating light to the phosphor. The radiation film with the recorded radiation image is supplied to a developing device to develop the radiation image, or the stimulable phosphor panel is supplied to a reading device to read the radiation image as a visible image.
In the operating room or the like, it is necessary to read recorded radiation image information immediately from a radiation conversion panel after the radiation image information is captured therein for the purpose of quickly and appropriately treating the patient. As a radiation conversion panel which meets such a requirement, there has been developed a direct-conversion-type radiation conversion panel for directly converting a radiation into an electric signal or an indirect-conversion-type radiation conversion panel which comprises a scintillator for temporarily converting a radiation into visible light and solid-state detectors for converting the visible light into an electric signal to read detected radiation image information.
It has been proposed in Japanese Laid-Open Patent Publication No. 2002-357664 to detect, with a load sensor, a load applied to the radiation-irradiated surface of a radiation detecting device which houses a radiation detector (radiation conversion panel) therein, and correct dark-current characteristics and sensitivity characteristics of the radiation conversion panel based on the detected load.
Japanese laid-open patent publication No. 2006-128890 discloses that the temperature status of a radiation conversion panel is grasped by detecting the temperature of the radiation conversion panel with a temperature sensor, and if the detected temperature deviates from a given temperature range, then a warning is issued and the radiation conversion panel is de-energized.
Japanese Laid-Open Patent Publication No. 2007-229366 reveals a radiation image capturing apparatus including an integral amplifier and an A/D converter which are connected to the output terminal of a radiation conversion panel.
Offsets and gain fluctuations of the integral amplifier and the A/D converter which are caused by temperature changes thereof are reduced.
For capturing radiation image information of a subject, the subject is held in contact with a radiation detecting apparatus, and a radiation is applied to the subject. While the subject is being irradiated with the radiation, i.e., while the radiation image information of the subject is being captured, the heat of the subject is transferred to a radiation conversion panel housed in the radiation detecting apparatus, increasing the temperature of the radiation conversion panel. Therefore, at least one of a sensitivity, a dark current, a density step, and a residual image of the radiation conversion panel tends to change.
However, Japanese Laid-Open Patent Publication No. 2002-357664, Japanese Laid-Open Patent Publication No. 2006-128890, and Japanese Laid-Open Patent Publication No. 2007-229366 fail to disclose or propose anything about temperature compensation for a change in at least one of the sensitivity, the dark current, the density step, and the residual image of the radiation conversion panel, which is caused by a temperature change of the radiation conversion panel.